Odd profiler behavior -- Kink

JerryFish

Can anyone help me explain why there would be a "kink" in profiler output, when the model (which includes a 4 parameter mixture) is a simple polynomial?

 

 

A customer asked about this.  If I drag the MC setting down, it hits the "kink" and drags the kink along.  So it has something to do with honoring the mixture constraint, but I don't know how to explain it in understandable terms.

 

Attaching a sample file if you want to play with it.  Script should duplicate the analysis, though you'll probably have to play with factor settings.

 

Thanks,

Jerry

 

Profile Kink Example.jmp

Dan_Obermiller

A few things.

 

First, the model is a polynomial, but is a cubic really a simple polynomial? Remember that the traditional 2-way interaction terms are quadratic model terms for a Scheffe mixture model. Also, the traditional 3-way interaction terms are cubic model terms for a Scheffe mixture model. So I would argue that this is not really that simple. It is a very "curvy" surface.

 

As for the kink, I think this is probably best seen by adding the Mixture Profiler and linking it with the Prediction Profiler. You will see that whenever you get to the edge of the design space (as shown on the mixture profiler), that is where you get a kink. The traditional "slope" from the profiler cannot continue because you have hit the boundary of the design space.